Differential viscometer

Detectors Model 410 differential refractive index (Waters Corporation) Model 100 differential viscometer (Viscotek Corporation) Dawn-F multiangle laser light-scattering photometer (Wyatt Technology)... 

Haney, M. A., The differential viscometer. II. On-line viscosity detector for size-exclusion chromatography, /. Appl. Polym. Sci., 30, 3037, 1985. 

Novolac molecular weights were measured in THF at 35°C by high pressure size exclusion chromatography using a Waters Model 510 pump (flow rate=1.0 ml/min), 401 differential viscometer detector and a set of Dupont PSM 60 silanized columns. A universal calibration curve was obtained with a kit of 10 narrow molecular weight distribution, linear polystyrene standards from Toya Soda Company. Data acquisition and analysis were performed on an AT T 6312 computer using ASYST Unical 3.02 software supplied with the Viscotek instrument. 

The size exclusion chromatography for this study was done in the routine manner execept for the inclusion of an online viscosity detector called a Differential Viscometer <3> (Viscotek Corp., Porter, Texas, USAl. This instrument together with an RI concentration detector permits the calculation of intrinsic viscosities across the chromatogram. An IBM PC data system with software is also provided (5). The software acquires data from both detectors, and performs calculations of intrinsic viscosity and molecular weight distributions using the Universal Calibration Method. 

Size exclusion chromatography has been greatly enriched recently by the advent of two commercial detectors, the real-time differential viscometer (DV) and the low angle laser light scattering (LALLS) photometer. The only DV detector currently available is offered by Viscotek in Porter, TX, as the model 100. 

A better approach is the use of two capillaries (Cl and C2) in series, each of which is connected to a differential pressure transducer (DPI and DP2), and a sufficiently large holdup reservoir (H) in between. With this approach, the sample viscosity q is measured from the pressure drop across the first capillary, and the solvent viscosity q0 from the pressure drop across the second capillary. Pulsations are eliminated in this setup because they appear in both transducers simultaneously. Another design is the differential viscometer, in which four capillaries are arranged similar to a Wheatstone bridge. In Fig. 10, both designs are shown schematically. 

The application of refractive index and differential viscometer detection in SEC has been discussed by a number of authors [66-68]. Lew et al. presented the quantitative analysis of polyolefins by high-temperature SEC and dual refractive index-viscosity detection [69]. They applied a systematic approach for multidetector operation, assessed the effect of branching on the SEC calibration curve, and used a signal averaging procedure to better define intrinsic viscosity as a function of retention volume. The combination of SEC with refractive index, UV, and viscosity detectors was used to determine molar mass and functionality of polytetrahydrofuran simultaneously [70]. Long chain branching in EPDM copolymers by SEC-viscometry was analyzed by Chiantore et al. [71]. 

Detection 1. Wyatt Technology Dawn-F MALLS with argon-ion laser at 514.5 nm 2. Viscotek differential viscometer 3. Differential refractive index... 

Use of molecular-weight-sensitive detectors (e.g., differential viscometer or light-scattering detector) eliminates the need for calibration. With a differential viscometer used as a detector for thermal FFF, the intrinsic viscosity is first measured for each retention time and is then converted to molecular weight using the Mark-Houwink constants [5]. The use of accurate... 

The first multiple-capillary viscometer was designed by the Viscotek Company (Houston, TX, U.S.A.) [7]. It is represented in Fig. lb. It is composed of four identical capillaries, assembled as a bridge. Here, the difference is generated by the bridge itself as a differential viscometer. The central DPT provides a differential viscosity signal DP and the second, DPT, provides inlet pressure IP. The intrinsic viscosity [17] can be calculated by the formula... 

The last differential viscometer design is the Waters Corporation detector [9], which is in the Alliance GPCV2000 high-temperature instrument. It is composed of three capillaries, two differential pressure transducers, and two holdup reservoirs it is represented in Fig. Id. The pressure transducers are connected flow-through this eliminates the need for frequent purges. This detector provides, at the same time, relative viscosity information and relative flow information. This design does not require a perfect matching of the capillaries. 

If all distributions of an HA sample (MMD, RGD, IVD) are required, use of absolute on-line detectors as MALS and Vise is needed. A multidetector SEC-LS-Visc system is composed of an LS detector (LALS or MALS), a viscometer (differential viscometer DV or SeV), and a concentration detector (DRI or UV). As a result, from the record of the on-line MALS detector, values of M and Rg can be obtained, while from the on-line Vise detector one can calculate [r)]. Fig. (9) shows the experimental relationships M = /(V), Rg = /(V), and [rj] = /(V) obtained using a SEC-MALS-SCV system for an HA sample (Mw =1314 kDa, D = 1.6). The use of absolute on-line detectors, as MALS and Vise, for the characterization of HA samples was described previously [270,279]. 

Viscotek Corp., 1032 Russell Drive, Porter, TX 77365 four-capillary and two-capillary differential viscometers. 

Poly (bis-trifluoro -ethoxy pho sphozene PL gels Cyclohexanone + 0.01 M tetrabutyl ammonium nitrate FALLS and differential viscometer Bimodal MW distril PMMA, and poly-T. 

Chromatograms of polybistrifluoroethoxyphosphazene using different detectors (a) differential refractometer, (b) differential viscometer, and (c) intrinsic viscosity. Column PLgel mixed bed. Mobile phase acetone, cyclohexanone. Temperature 30°C, 40°C. [From T. H. Mourey et al. (1989)... 

The only universal detector sensitive enough to detect asphalt (because of its relatively low molecular weight) is the Viscotek differential viscometer (108,109). It utilizes a Wheatstone bridge flow resistance scheme that measures intrinsic viscosity differences between the column eluant and the carrier solvent. Other viscosity detectors measure absolute intrinsic viscosity of the eluant and are not as precise. In Figure 19, several supercritically refined asphalt fractions having a variety of molecular weights (MJ are seen to have similar RI and IV... 

Universal calibration curve established with a Viseotek Model 100 differential viscometer detector. Calibration standards are narrowly distributed pullulans at 0.12% concentration. All other eonditions as in Figure 8. 

---